TLR-dependent formation of multinucleated giant cells

在分枝杆菌感染中，多核巨细胞（MGCs）在一个严格调控的过程中从巨噬细胞中产生，该过程仅限于多细胞肉芽肿。在前三年的资助中，我们已经描述了Toll样受体2激活通过诱导复制应激和DNA损伤反应导致修饰的细胞分裂和有丝分裂缺陷来指导多倍体MGC。这个过程中的一个重要中间体是一氧化氮，它会导致DNA损伤并损害p53功能。因此，分枝杆菌似乎矛盾地通过驱动转化为许可的MGCs而从抗菌努力中获益。在接下来的三年里，我们的目标是进一步确定MGC形成的分化机制，因为它们形成了合理的治疗靶点。我们的中心假设是，共同的单核细胞祖细胞（cMoPs）是专门的MGC前体。伴随着骨髓流出和募集到感染部位，cMoPs获得了一种新的表型，表达典型的单核细胞表面标志物，但保留了增殖能力和MGC前体潜力。此外，我们提出髓系转录因子IRF8对于完整的抗菌MGC功能是必不可少的。具体目的是a）定义在源自cMoPs的MGC的形成和功能中的转录程序，B）定义IRF 8在组织巨噬细胞发育中的定性作用，和c）分析MGC中的免疫代谢。破译MGC形成的细胞和转录先决条件，缺乏IRF8作为分枝杆菌感染的免疫缺陷模型，有望揭示增强抗分枝杆菌免疫力的新策略。

In mycobacterial infections multinucleated giant cells (MGCs) arise from macrophages in a tightly regulated process, which is confined, to multicellular granulomas. In the first three years of funding we have delineated that Toll-like receptor 2 activation instructs polyploid MGC via induction of replication stress and a DNA damage response leading to modified cell divisions and mitotic defects. An important intermediate in this process is nitric oxide, which causes DNA damage and impairs p53 function. Thus mycobacteria appear to paradoxically profit from antimicrobial efforts by driving transformation into permissive MGCs. In the upcoming three years we aim at further defining differentiation mechanisms underlying MGC formation, since they form rational therapeutic targets. Our central hypothesis is that common monocyte progenitors (cMoPs) are dedicated MGC precursors. Concomitant to bone-marrow egress and recruitment to the site of infection, cMoPs acquire a novel phenotype with expression of typical monocyte surface markers, yet preservation of proliferative capacity and MGC precursor potential. Moreover, we propose that the myeloid transcription factor IRF8 is essential for full antimicrobial MGC function. The specific aims are a) to define the transcriptional program in the formation and function of MGC originating from cMoPs, b) to define the qualitative role of IRF8 in the development of tissue macrophages, and c) to analyze immunometabolism in MGC. Deciphering the cellular and transcriptional preconditions for MGC formation, with lack of IRF8 as a model immunodeficiency for mycobacterial infections, is expected to reveal novel strategies to boost antimycobacterial immunity.